This invention relates to a process for easily detecting an air resident in a liquid-charged transparent receptacle, especially the air that floats above the liquid contained in the receptacle and is difficult to detect it by the eye from the outside because the view of air is interrupted by an opaque seal member attached to the mouth portion of the receptacle.
Recently, in the fields of medical treatment, for instance dental treatment and the like there is being used a receptacle which comprises charging the transparent receptacle 1 shown in FIG. 1A and FIG. 1B with an anesthetic or the like, plugging its bottom portion with a rubber plug 2 which is also usable as pistons, covering a mouth portion with a rubber film 3, and sealing it with an opaque seal member 4 such as an aluminum foil. In the practical use of this receptacle, a rear end of an injection needle (not shown) is injected in the rubber film 3, the rubber plug 2 is used as a piston, and consequently the receptacle 1 itself is used in the same manner as the usual injector. Accordingly, upon charging the liquid, it is not permitted to use a receptacle containing the air over the prescribed amount. Such receptacles must be abolished as inferior goods. This resident air, as shown in FIG. 1A, forms an air cavity 5 on the top portion of the liquid at the mouth portion of the receptacle and resides therein. However, as it is difficult to detect it by the eye from the outside because its view is obstructed by the seal member 4, in order to detect the air workers have made it a rule to hold it upside down, give it a shock for transferring the air toward the rubber plug 2 located upward, and detecting the air by the eye.
However, the detecting process like this, as is apparent from the aforegoing, was defective in that its operation is very complicated, it is extremely inefficient, and further a fixed accuracy can not be obtained.